UPDATE: New album with additional photos here: http://imgur.com/a/RGfrP
My parent's house has a pretty bad leak that has been going for a few years. Because of money and other issues with the house I need to try do an improvement myself if at all possible. Getting a new roof (or house, since everything else is outdated/has an issue) may be possible down the line but not right now.
One thing slightly in my favor is this is in San Diego so it rains infrequently.
I have included some pictures. In the last you can see where I pulled some of the ceiling down where it was mostly soft/mushy. Asbestos test was negative.
Estimators have suggested the issue is definitely with the valley and one of them recommended I could install flashing in/along/under (not sure what he meant) the valley to improve the situation. I purchased a roll of aluminum flashing. I am not clear on exactly where to put it though.
The examples I see on youtube when I search 'roof valley' don't have such a low slope or the part where it goes up/horizontally again like that. The ones I saw were mostly just one smooth seem. If it was like that then I have some tutorials on doing underlayment, flashing, trimming shingles for a normal valley. But I haven't seen an example quite like my roof.
Thanks so much for any advice.